This invention relates to external fixation elements, especially to external fixation rods. More particularly, it relates to an apparatus and method to make use of such elements safer during MRI procedures.
Magnetic Resonance Imaging (MRI) is a well known diagnostic tool in the field of medicine. It is equally known to surgeons that problems may occur for patients wearing metallic devices inside or outside their body during examination with a MRI device (inside or outside the coil).
It is known in the prior art, e.g. from FR 2 703 580, to use antimagnetic implants, e.g. made in polyethylene, and to use additional radiopaque markers to get an image of the implant. This makes such an implant MRI-safe.
U.S. Publication No. 2002/042619 discloses a headframe for use with a stereotactic system. It is mentioned in the last paragraph of the description that the frame body and swivel arms need not to be made from aluminum. Instead, the frame body and swivel arms as well as other components of the headframe may be formed of a non-magnetic material such as plastic, ceramic, or other composite such that the headframe is compatible with MRI, CT, X-ray and magnetic stereotactic device/procedures.
In the field of elements constituting an external fixation device or to be used with an external fixation device it is known to use rods of, for example, stainless steel. However, the use of such ferromagnetic rods does not allow MRI examinations. As an alternative, rods of aluminum or of carbon fibers may be used. Rods made from the latter named materials are not ferromagnetic. However, within the field of external fixation, the combination of these elements, e.g. rods with clamps and pins, constitute either along or together with the body of the patient a closed conductive loop.
For MRI safety, it is equally important not to interfere with the static field, the gradient field as well as the RF-field, therefore such external fixation elements cannot be used in MRI environments.